In this work under-mask penetration of Al+ ions implanted in 4H-SiC is investigated by computer simulation based on the Monte-Carlo binary collision approximation (MC–BCA). Results indicate that a small fraction of ions, implanted normal to a (0001) 4H-SiC wafer (8 off-axis towards the {11-20}), is scattered and become channeled in the< 1120> directions perpendicular to the< 0001> axis. Due to this phenomenon, doped regions with concentration≤ 10− 4 of the peak value, may extend laterally for a few µm below the edge of a SiO2 mask.